The invention relates generally to methods and apparatus for reconstructing blood vessels, and particularly to methods and apparatus for three-dimensional reconstructions.
The present invention relates to methods for reconstructing blood vessels based on position information acquired from a position sensor contained in a catheter that traverses the vessel.
Blood vessels are visualized today principally by angiography, in which a contrast medium is injected into the bloodstream and the vasculature is imaged using ionizing radiation imaging modalities. Such imaging must be limited however, due to the adverse effects of cumulative radiation on patients. Furthermore, some patients react adversely to the contrast media used in angiography. Accordingly, it would be desirable to have a visualization method that does not depend on ionizing radiation imaging modalities or on the use of contrast agents.
U.S. Pat. No. 5,546,951 and U.S. patent application No. 08/793,371, which are incorporated herein in their entirety by reference, disclose methods for sensing an electrical property of the heart tissue, for example, local activation time, as a function of the precise location within the heart. The data are acquired with one or more catheters that are advanced into the heart, the catheters having electrical and location sensors in their distal tips. Methods of creating a map of the electrical activity of the heart based on these data are disclosed in commonly assigned U.S. patent applications No. 09/122,137 and 09/357,559 filed on Jul. 24, 1998 and Jul. 22, 1999, respectively, which are also incorporated herein in their entirety by reference. As indicated in these applications, location and electrical activity is preferably initially measured on about 10 to about 20 points on the interior surface of the heart. These data points are then generally sufficient to generate a preliminary reconstruction or map of the cardiac surface to a satisfactory quality. The preliminary map is formed by defining an initial, closed 3-dimensional curved surface, preferably of an ellipsoid, in a reconstruction space in the volume of the sample points. The closed curve is roughly adjusted to a shape which resembles a reconstruction of the sample points. Thereafter, a flexible matching stage is repeatedly performed one or more times to bring the closed curve to resemble the shape of the actual volume being reconstructed. While the above-described methods provide satisfactory reconstructions of organs, the algorithms employed therein do not provide accurate reconstructions of blood vessels, particularly when the vessels are convoluted or tortuous in shape.
Reconstruction of blood vessels in images or reconstructions of the heart are beneficial because the blood vessels provide confirmatory landmarks that assist in navigation to specific regions in the heart. Accordingly, it would be desirable to have a method of realistically reconstructing blood vessels that complements existing methods for reconstructing chambers of the heart.
Cardiologists are increasingly attributing atrial fibrillation to defects in the electrical pathways of the heart that originate in the pulmonary vein. Diagnosis and treatment of this condition requires assessing the electrical activity in the pulmonary vein and subsequently ablating defects in or around the vein. Methods for reconstructing the veins with data that may be accumulated with catheters bearing diagnostic or therapeutic components would facilitate the use and outcomes of these procedures.
Certain interventional and diagnostic procedures such as catheterization of the brain are preceded by the generation of images of the vasculature by modalities such as magnetic resonance imaging (MRI). A reconstruction of the vessels effected during the catheterization that could be registered with a previously acquired image would allow the physician to identify the catheter tip location during the procedure with respect to the previously acquired image.
The present invention is directed to a method for reconstructing the inner surface of a blood vessel using a catheter having a position sensor contained therein. The method of the invention comprises the following steps:
a) advancing the catheter into the vessel;
b) acquiring position information from the sensor at a plurality of points in the vessel;
c) calculating a center-line of the vessel based on said position information; and
d) calculating the inner surface of the vessel.
In a preferred embodiment, the method of the invention further comprises the step of displaying the reconstructed vessel surface.
The invention is also directed to apparatus for reconstructing the inner surface of vessels, which comprises:
a) a catheter having a position sensor contained therein;
b) means for acquiring position information from said sensor at a plurality of points in said vessel;
c) means for calculating a centerline of the vessel based on said position information; and
d) means for calculating the inner surface of the vessel.
In a preferred embodiment, the apparatus of the invention further comprises means for displaying the vessel reconstruction.
It is an object of the invention to provide a method and apparatus for reconstructing blood vessels without the use of imaging modalities or contrast agents.
It is another object of the invention to provide a method of reconstructing blood vessels that is complementary to methods and apparatus for reconstructing the heart.
It is another object of the invention to provide a method of vessel reconstruction that could provide reconstructions that could be registered with previously acquired images of the vasculature.
These and other objects, features and advantages of the present invention will be more readily apparent for the detailed description set forth below, taken in conjunction with the accompanying drawings.